When CONFIG_LOCKDEP is set, every use of DECLARE_WAIT_QUEUE_HEAD_ONSTACK()
produces an bogus warning from clang, which is particularly annoying
for allmodconfig builds:
fs/namei.c:1646:34: error: variable 'wq' is uninitialized when used within its
own initialization [-Werror,-Wuninitialized]
DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
^~
include/linux/wait.h:74:63: note: expanded from macro
'DECLARE_WAIT_QUEUE_HEAD_ONSTACK'
struct wait_queue_head name = __WAIT_QUEUE_HEAD_INIT_ONSTACK(name)
~~~~ ^~~~
include/linux/wait.h:72:33: note: expanded from macro
'__WAIT_QUEUE_HEAD_INIT_ONSTACK'
({ init_waitqueue_head(&name); name; })
^~~~
A patch for clang has already been proposed and should soon be
merged for clang-9, but for now all clang versions produce the
warning in an otherwise (almost) clean allmodconfig build.
Link: https://bugs.llvm.org/show_bug.cgi?id=31829
Link: https://bugs.llvm.org/show_bug.cgi?id=42604
Link: https://lore.kernel.org/lkml/[email protected]/
Link: https://reviews.llvm.org/D64678
Link:
https://storage.kernelci.org/next/master/next-20190717/arm64/allmodconfig/clang-8/build-warnings.log
Suggested-by: Nathan Chancellor <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
---
v2: given that kernelci is getting close to reporting a clean build for
clang, I'm trying again with a less invasive approach after my
first version was not too popular.
---
include/linux/wait.h | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/include/linux/wait.h b/include/linux/wait.h
index ddb959641709..276499ae1a3e 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -70,8 +70,17 @@ extern void __init_waitqueue_head(struct wait_queue_head
*wq_head, const char *n
#ifdef CONFIG_LOCKDEP
# define __WAIT_QUEUE_HEAD_INIT_ONSTACK(name) \
({ init_waitqueue_head(&name); name; })
-# define DECLARE_WAIT_QUEUE_HEAD_ONSTACK(name) \
+# if defined(__clang__) && __clang_major__ <= 9
+/* work around https://bugs.llvm.org/show_bug.cgi?id=42604 */
+# define DECLARE_WAIT_QUEUE_HEAD_ONSTACK(name)
\
+ _Pragma("clang diagnostic push")
\
+ _Pragma("clang diagnostic ignored \"-Wuninitialized\"")
\
+ struct wait_queue_head name = __WAIT_QUEUE_HEAD_INIT_ONSTACK(name)
\
+ _Pragma("clang diagnostic pop")
+# else
+# define DECLARE_WAIT_QUEUE_HEAD_ONSTACK(name) \
struct wait_queue_head name = __WAIT_QUEUE_HEAD_INIT_ONSTACK(name)
+# endif
#else
# define DECLARE_WAIT_QUEUE_HEAD_ONSTACK(name) DECLARE_WAIT_QUEUE_HEAD(name)
#endif
--
2.20.0
